The present invention relates to golf balls and more particularly, the invention is directed to a golf ball having a non-uniform thickness layer.
Conventional golf balls can be divided into two general types or groups: solid balls or wound balls. The difference in play characteristics resulting from these different constructions can be quite significant. These balls, however, have primarily two functional components that make them work. These components are the center or core and the cover. The primary purpose of the core is to be the xe2x80x9cspringxe2x80x9d of the ball or the principal source of resiliency. The cover protects the core and improves the spin characteristics of the ball.
Two-piece solid balls are made with a single-solid core, usually made of a cross-linked polybutadiene or other rubber, which is encased by a cover. These balls are typically the least expensive to manufacture as the number of components is low and these components can be manufactured by relatively quick, automated molding techniques. In these balls, the solid core is the xe2x80x9cspringxe2x80x9d or source of resiliency. The resiliency of the core can be increased by increasing the cross-linking density of the core material. As the resiliency increases, however, the compression also increases making a harder ball, which is undesirable. Recently, commercially successful golf balls, such as the Titleist Pro-VI golf balls, have a relatively large polybutadiene based core, ionomer casing and polyurethane cover, for long distance when struck by the driver clubs and controlled greenside play.
Moreover, the spin rate of golf balls is the end result of many variables, one of which is the distribution of the density or specific gravity within the ball. Spin rate is an important characteristic of golf balls for both skilled and recreational golfers. High spin rate allows the more skilled players, such as PGA professionals and low handicapped players, to maximize control of the golf ball. A high spin rate golf ball is advantageous for an approach shot to the green. The ability to produce and control back spin to stop the ball on the green and side spin to draw or fade the ball substantially improves the player""s control over the ball. Hence, the more skilled players generally prefer a golf ball that exhibits high spin rate.
On the other hand, recreational players who cannot intentionally control the spin of the ball generally do not prefer a high spin rate golf ball. For these players, slicing and hooking are the more immediate obstacles. When a club head strikes a ball, an unintentional side spin is often imparted to the ball, which sends the ball off its intended course. The side spin reduces the player""s control over the ball, as well as the distance the ball will travel. A golf ball that spins less tends not to drift off-line erratically if the shot is not hit squarely off the club face. The low spin ball will not cure the hook or the slice, but will reduce side spin and its adverse effects on play. Hence, recreational players prefer a golf ball that exhibits low spin rate.
However, the prior art does not disclose a golf ball that has a large core or xe2x80x9cspringxe2x80x9d and a high specific gravity, non-uniform thickness layer for controlled spin.
The present invention is directed to a golf ball with a controlled moment of inertia.
The present invention is preferably directed to a golf ball comprising an intermediate layer covering a core, wherein the intermediate layer is encased by a cover, wherein the intermediate layer comprises a non-uniform thickness layer, a maximum thickness in the range of about 0.010 inch to about 0.150 inch and a flexural modulus of greater than about 80,000 psi. The non-uniform thickness layer may comprise a plurality of projections disposed thereon, a plurality of longitudinal webs, a plurality of latitudinal webs, or a plurality of circumferential webs. Preferably, the maximum thickness of the non-uniform thickness layer is in the range of about 0.015 inch to about 0.100 inch. The profile of the projections is selected from a group consisting of trapezoidal, sinusoidal, dome, stepped, cylindrical, conical, truncated conical, rectangular, pyramidal with polygonal base, truncated pyramidal and polyhedronal. Alternatively, the non-uniform thickness layer comprises outer projections or inner projections.
Another aspect of the present invention is directed to a golf ball comprising an intermediate layer covering a core, wherein the intermediate layer is encased by a cover, wherein the intermediate layer comprises a continuous layer having non-uniform thickness, a specific gravity of at least about 1.2 and a moment of inertia of at least about 0.46 ozxc2x7inch2. The specific gravity of the non-uniform thickness layer may be at least about 1.5 or preferably at least about 2.0. The maximum thickness of the non-uniform thickness layer is preferably in the range of about 0.010 inch to about 0.150 inch, and more preferably in the range of about 0.015 inch to about 0.100 inch. Additionally, the flexural modulus of the non-uniform thickness layer is greater than about 30,000 psi, more preferably greater than about 50,000 psi and even more preferably greater than about 75,000 psi.
Preferably, the non-uniform thickness layer comprises a plurality of projections, and the profile of the projections is selected from a group consisting of trapezoidal, sinusoidal, dome, stepped, cylindrical, conical, truncated conical, rectangular, pyramidal with polygonal base, truncated pyramidal and polyhedronal. The projections can be outer or inner projections. Alternatively, the non-uniform thickness layer may comprise webs.
Another aspect of the invention is directed to a golf ball comprising an intermediate layer covering a core, wherein the intermediate layer is encased by a cover, wherein the intermediate layer comprises a non-uniform thickness layer having a plurality of circular webs disposed, thereon such that the webs increase the stiffness of the intermediate layer and wherein the ball has a coefficient of restitution of at least 0.76 at 160 feet per second. The compression of the core and intermediate layer is at least about 60 PGA, preferably at least about 80 PGA and more preferably at least about 90 PGA. The webs may be longitudinal webs, latitudinal webs or circumferential webs. The webs can be inner or outer webs. Preferably the flexural modulus of the non-uniform thickness layer is less than 30,000 psi. The golf ball also preferably has a coefficient of restitution is at least 0.80 at 125 feet per second.
The golf ball of the present invention may also comprise a second non-uniform thickness layer.